The primary goal of our research program continues to be the elucidation of the principles that govern the ways in which mucleic acids fold and interact with other molecules. We will do this by determining and analyzing the crystal structures of selected oligonucleotides and oligonucleotide/small molecule complexes. Our studies of DNA-small molecule interactions will include: 1) the determination of the structure of a complex between the drug actinomycin D and and a DNA fragment in an attempt to understand the molecular basis for its antitumor and antibiotic activities; 2) the determination of the structures of DNA fragments to which the chemotherapeutic agent mitomycin C have been bound; and 3) the determinations of structures of complexes between the chiral specific probe RuDIP and left and right handed DNA. In addition we will be studing the effects of sequence on the structure of DNA by determining the crystal structures of several selected oligonucleotides.